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  Subjects -> ENGINEERING (Total: 2284 journals)
    - CHEMICAL ENGINEERING (192 journals)
    - CIVIL ENGINEERING (184 journals)
    - ELECTRICAL ENGINEERING (102 journals)
    - ENGINEERING (1208 journals)
    - ENGINEERING MECHANICS AND MATERIALS (389 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (65 journals)
    - MECHANICAL ENGINEERING (89 journals)

CHEMICAL ENGINEERING (192 journals)                     

Showing 1 - 192 of 192 Journals sorted alphabetically
AATCC Journal of Research     Full-text available via subscription   (Followers: 6)
ACS Sustainable Chemistry & Engineering     Hybrid Journal   (Followers: 5)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 5)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Additives for Polymers     Full-text available via subscription   (Followers: 20)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 7)
Advanced Chemical Engineering Research     Open Access   (Followers: 31)
Advanced Powder Technology     Hybrid Journal   (Followers: 16)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 5)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 24)
Advances in Chemical Engineering and Science     Open Access   (Followers: 53)
Advances in Polymer Technology     Hybrid Journal   (Followers: 13)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 10)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 9)
Applied Petrochemical Research     Open Access   (Followers: 2)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 7)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 14)
Biofuel Research Journal     Open Access   (Followers: 4)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 3)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Catalysts     Open Access   (Followers: 7)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
Chemical and Engineering News     Free   (Followers: 12)
Chemical and Materials Engineering     Open Access   (Followers: 13)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 12)
Chemical and Process Engineering     Open Access   (Followers: 27)
Chemical and Process Engineering Research     Open Access   (Followers: 24)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 32)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 17)
Chemical Engineering and Science     Open Access   (Followers: 19)
Chemical Engineering Communications     Hybrid Journal   (Followers: 14)
Chemical Engineering Education     Full-text available via subscription  
Chemical Engineering Journal     Hybrid Journal   (Followers: 36)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 23)
Chemical Engineering Research Bulletin     Open Access   (Followers: 12)
Chemical Engineering Science     Hybrid Journal   (Followers: 27)
Chemical Geology     Hybrid Journal   (Followers: 18)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 4)
Chemical Reviews     Full-text available via subscription   (Followers: 174)
Chemical Society Reviews     Full-text available via subscription   (Followers: 41)
Chemical Technology     Open Access   (Followers: 16)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Industry     Hybrid Journal   (Followers: 5)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry of Materials     Full-text available via subscription   (Followers: 241)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 15)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 4)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal  
Computational Biology and Chemistry     Hybrid Journal   (Followers: 12)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 9)
CORROSION     Full-text available via subscription   (Followers: 20)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 35)
Corrosion Reviews     Hybrid Journal   (Followers: 5)
Crystal Research and Technology     Hybrid Journal   (Followers: 6)
Current Opinion in Chemical Engineering     Open Access   (Followers: 7)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
Eksergi     Open Access  
Emerging Trends in Chemical Engineering     Full-text available via subscription   (Followers: 3)
European Polymer Journal     Hybrid Journal   (Followers: 41)
Fibers and Polymers     Full-text available via subscription   (Followers: 6)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 2)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 2)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 6)
Heat Exchangers     Open Access   (Followers: 3)
High Performance Polymers     Hybrid Journal   (Followers: 1)
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 5)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 10)
Indonesian Journal of Chemical Science     Open Access   (Followers: 1)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 11)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 21)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Gases     Open Access  
Info Chimie Magazine     Full-text available via subscription   (Followers: 3)
International Journal of Chemical and Petroleum Sciences     Open Access   (Followers: 3)
International Journal of Chemical Engineering     Open Access   (Followers: 7)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 3)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access   (Followers: 1)
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 6)
International Journal of Science and Engineering     Open Access   (Followers: 3)
International Journal of Waste Resources     Open Access   (Followers: 4)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 5)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 6)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 13)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 177)
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 11)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 6)
Journal of Chemical Engineering     Open Access   (Followers: 20)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 2)
Journal of Chemical Science and Technology     Open Access   (Followers: 4)
Journal of Chemical Sciences     Partially Free   (Followers: 19)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 10)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 15)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 2)
Journal of Combinatorial Chemistry     Full-text available via subscription  
Journal of Crystallization Process and Technology     Open Access   (Followers: 8)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 5)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access   (Followers: 1)
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Geochemical Exploration     Hybrid Journal   (Followers: 1)
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Hybrid Journal   (Followers: 1)
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 9)
Journal of Modern Chemistry & Chemical Technology     Full-text available via subscription   (Followers: 2)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 6)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 8)
Journal of Organic Semiconductors     Open Access   (Followers: 5)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 5)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 6)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 9)
Journal of Polymer Research     Hybrid Journal   (Followers: 6)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 6)
Journal of Polymers     Open Access   (Followers: 6)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 2)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 296)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 1)
Journal of the Pakistan Institute of Chemical Engineers     Open Access   (Followers: 1)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 9)
Jurnal Bahan Alam Terbarukan     Open Access  
Jurnal Inovasi Pendidikan Kimia     Open Access   (Followers: 5)
Jurnal Reaktor     Open Access  
Jurnal Rekayasa Kimia & Lingkungan     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Konversi     Open Access  
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 1)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 16)
Materials Science and Applied Chemistry     Open Access  
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Modern Chemistry & Applications     Open Access  
Molecular Imprinting     Open Access  
Nanochemistry Research     Open Access  
Nanocontainers     Open Access   (Followers: 1)
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 4)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 4)
Plasma Processes and Polymers     Hybrid Journal   (Followers: 3)
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 122)
Polymer Bulletin     Hybrid Journal   (Followers: 7)
Polymer Composites     Hybrid Journal   (Followers: 15)
Polyolefins Journal     Open Access  
Powder Technology     Hybrid Journal   (Followers: 13)
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 61)
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Open Access   (Followers: 2)
South African Journal of Chemistry     Open Access   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 5)
Sustainable Chemical Processes     Open Access   (Followers: 2)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 2)
Transition Metal Chemistry     Hybrid Journal   (Followers: 4)
Transylvanian Review of Systematical and Ecological Research     Open Access  
Visegrad Journal on Bioeconomy and Sustainable Development     Open Access   (Followers: 2)
Zeitschrift für Naturforschung B : A Journal of Chemical Sciences     Open Access   (Followers: 1)

           

Journal Cover Chemical Engineering Science
  [SJR: 1.073]   [H-I: 135]   [27 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [3042 journals]
  • Modelling microbial transport in simulated low-grade heap bioleaching
           systems: The hydrodynamic dispersion model
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Elaine Govender-Opitz, Athanasios Kotsiopoulos, Christopher G. Bryan, Susan T.L. Harrison
      The hydrodynamic model was developed to describe microbial growth kinetics within heap bioleaching systems. Microbial partitioning between the bulk flowing pregnant leach solution (PLS) and ore-associated phases that exist within the low-grade chalcopyrite ore bed, as a function of microbial transport between these identified phases, was investigated. Microbial transport between the bulk flowing PLS and ore-associated phases was postulated to be driven by the microbial concentration gradient between the phases, with advection and dispersion forces facilitating microbial colonisation of, and transport through, the ore bed. The population balance model (PBM) was incorporated into the hydrodynamic model to estimate mineral dissolution rates as a function of available surface area appropriately. Temporal and spatial variations in microbial concentration in the PLS and ore-associated phases are presented together with model predictions for overall ferrous and ferric iron concentrations, which account for iron concentrations in the bulk flowing PLS and that in the vicinity of the mineral surface. The model predictions for PLS and ore-associated microbial concentrations are validated with experimental data, demonstrating the improvement of this model over the previously presented ‘biomass model’. Based on Michaelis-Menten type kinetics, model-predicted true maximum specific growth rates for Acidithiobacillus ferrooxidans in the PLS and ore-associated phases were found to be 0.0004 and 0.019h−1, respectively. Estimated microbial attachment and detachment rates suggest that microbial growth is more prolific in the ore-associated phases with subsequent transport to the bulk flowing PLS. Sensitivity analysis of the hydrodynamic transport model to changes in the advection mass transfer coefficient, dispersion coefficient and inoculum size are discussed. For the current reactor configuration, increasing the irrigation rate from 2 to 2.5Lm−2 h−1, i.e. increasing the advection mass transfer rate, resulted in a significant decrease in microbial retention within the ore bed.

      PubDate: 2017-07-22T22:07:17Z
       
  • Novel glucose-based adsorbents (Glc-As) with preferential adsorption of
           ethane over ethylene and high capacity
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Chen Ma, Xingjie Wang, Xun Wang, Binqin Yuan, Yufang Wu, Zhong Li
      In this work, we reported novel glucose-based adsorbents (Glc-As) with high C2H6/C2H4 adsorption capacity and selectivity. Starch sugar (e.g., glucose, 50wt%) was used as carbon source to prepare novel glucose-based carbon materials for C2H6/C2H4 separation. The BET surface area of the resulting Glc-As can reach as high as 2073m2/g, and their pore diameters fell into the region of micropores benefiting adsorption of light hydrocarbons. FTIR spectra and XPS were applied to analysize the surface chemistry of the samples. It showed the presence of O functionalities in Glc-As, and its contents decreased with increasing KOH/C ratio at which the sample was activated. Glc-As achieved superior high C2H6 adsorption capacity of 7.98mmol/g at 288K and 1bar, which was benefited from the abundant micropores. More importantly, Glc-As exhibited greatly preferential adsorption of C2H6 over C2H4, with the C2H6/C2H4 adsorption selectivity in the range of 2.02–5.98 at pressure below 100kPa, higher than most reported adsorbents possessing preferential adsorption of C2H6 over C2H4. This could ascribe to the higher polarizability and larger kinetic diameter of C2H6, resulting in its stronger interaction with the pore surfaces of Glc-As compared to C2H4, and exhibiting in significantly preferential adsorption of ethane over ethylene. Besides, adsorption heat calculation showed that the isosteric heats of C2H6 adsorption on Glc-As were higher than the isosteric heats of C2H4. Fixed bed experiments showed that C2H4/C2H6 mixture can be well separated in the fixed bed packed with Glc-As. In sum, Glc-As as new carbon materials possess not only excellent stability, but also excellent adsorption properties for separation of C2H6 and C2H4, It would be promising adsorbents for the effective separation of ethane/ethylene.
      Graphical abstract image

      PubDate: 2017-07-22T22:07:17Z
       
  • Study of bubble dynamics in gas-solid fluidized beds using ultrashort echo
           time (UTE) magnetic resonance imaging (MRI)
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Hilary T. Fabich, Andrew J. Sederman, Daniel J. Holland
      A narrow column, gas-solid fluidized bed was studied using ultrashort echo time (UTE) magnetic resonance imaging (MRI) for particles of diameter 0.44mm, 0.72mm, and 1.5mm. UTE enables 1D and 2D images to be acquired of an individual bubble as it rises through the sample with higher spatial resolution than has previously been possible with MRI. One-dimensional images allow calculations of bubble rise velocity and bubble frequency. They also show leading-trailing bubble coalescence. Images of bubbles in the axial plane were obtained in 2D, with the location of images adjusted to track bubbles as they rise. These measurements were used to observe the wake region of a bubble, lateral drift as the bubble rises, and in-plane bubble coalescence. Images in the vertical plane were used to study the stability of a 1D perturbation in voidage. The perturbation collapsed rapidly with particles <1mm in diameter, but for the 1.5mm diameter particles the perturbation was often stable throughout the imaging region.

      PubDate: 2017-07-22T22:07:17Z
       
  • Modelling of paste ram extrusion subject to liquid phase migration and
           wall friction
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): M.J. Patel, S. Blackburn, D.I. Wilson
      Extrusion of solid-liquid particulate pastes is a well-established process in industry for continuously forming products of defined cross-sectional shape. At low extrusion velocities, the solids and liquid phases can separate due to drainage of liquid through the interparticle pores, termed liquid phase migration (LPM). The effect of wall friction, die shape and extrusion speed on LPM in a cylindrically axisymmetric ram extruder is investigated using a two-dimensional finite element model of paste extrusion based on soil mechanics principles (modified Cam-Clay). This extends the smooth walled model reported by Patel et al. (2007) to incorporate a simplified Tresca wall friction condition. Three die entry angles (90°, 60° and 45°) and two extrusion speeds are considered. The extrusion pressure is predicted to increase with the Tresca friction factor and the extent of LPM is predicted to increase with decreasing ram speed (both as expected). The effects of wall friction on LPM are shown to be dictated by the die shape and ram displacement: there are few general rules relating extruder design and operating conditions to extent of LPM, so that finite element-based simulation is likely to be needed to predict the onset of LPM accurately.

      PubDate: 2017-07-22T22:07:17Z
       
  • Adaptive just-in-time and relevant vector machine based soft-sensors with
           adaptive differential evolution algorithms for parameter optimization
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Yiqi Liu
      Just-in-time (JIT) and Relevant vector machine (RVM) are two of commonly used models for soft-sensors modeling, the efficiency of which is governed by few critical parameters and hyper-parameters significantly. These parameters are routinely selected by trial and error or experience, thus leading to over- or under-fitting for the prediction. Adaptive differential evolution with optional external archive (JADE) has been used to optimize the parameters of JIT and RVM in this paper. The resulted JADE-JIT and JADE-RVM based soft-sensors are further enhanced into an adaptive format by the moving window (WM) technique. The proposed methodologies are applied to prediction of hard-to-measured variables in the wastewater treatment plants (WWTPs) and successful results are obtained.

      PubDate: 2017-07-22T22:07:17Z
       
  • Modelling of the flow of ellipsoidal particles in a horizontal rotating
           drum based on DEM simulation
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Huaqing Ma, Yongzhi Zhao
      The granular flow involving ellipsoidal particles in a horizontal rotating drum is investigated by DEM, in which ellipsoidal particle is modeled by super-ellipsoids and periodic boundary condition is adopted. Recurring to the abundant information obtained from the DEM simulation, a comparably synthetical investigation is performed for the better understanding of the fundamental of the granular flow involving ellipsoidal particles in a horizontal rotating drum. All cases utilized in this work are characterized by the continuous flow, namely in rolling/cascading regime. How the aspect ratio and the rotation speed of the drum influence the transverse mixing is surveyed. And some attempt has been made to elucidate the above influence on the particle mixing from the perspective of particle diffusion and particle convection. A brief description about the influence of the aspect ratio and rotation speed of the drum on the axis dispersion is also provided. The Euler angles, including the precession angle, nutation angle and spin angle, are utilized to study the distribution profiles of the orientation for ellipsoidal particles. Simultaneously, some simple methods have been devised for different investigation purposes involving particle orientation.
      Graphical abstract image

      PubDate: 2017-07-22T22:07:17Z
       
  • Segregation dynamics of a binary-size mixture in a three-dimensional
           rotating drum
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Shiliang Yang, Yuhao Sun, Liangqi Zhang, Jia Wei Chew
      The knowledge of the granular segregation phenomenon induced by size or density differences in the ubiquitous polydisperse systems is important, hence numerous studies have focused on this for the simple yet practical rotating drum. However, in view of the distinctly different characteristics of the two regions (namely, active and passive) for a drum operated in the rolling regime, an understanding of the segregation dynamics in each region is warranted, but remains a gap to date. Accordingly, this study aimed at numerically studying the segregation dynamics of the solid phase in a three-dimensional rotating drum consisting of a binary-size mixture via the Discrete Element Method (DEM). The results demonstrate that the total kinetic energy, the angle of repose, the time-averaged streamwise (i.e., parallel to the bed surface) velocity and the position of the active-passive interface are global parameters, which are not influenced by size-segregation and thereby provides a critical basis for comparing different systems of various polydispersities. Also, the quick onset of the rapid radial segregation leads to sharp initial changes of the variables associated with the two particle types, after which the slow axial segregation leads to a gradual change of these variables over time. Furthermore, size-segregation leads to the redistribution of the particle number of the two particle types in the active and passive regions. Relative to the monodisperse system, the collision forces exerted on the small and large particles are slightly higher and lower, respectively. The results here provide important insights on the dynamics associated with the inevitable segregation phenomenon, which contributes to better operation and predictive capability of the rotating drum.

      PubDate: 2017-07-22T22:07:17Z
       
  • Analysis of particle-laden fluid flows, tortuosity and particle-fluid
           behaviour in metal foam heat exchangers
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Sahan T.W. Kuruneru, Emilie Sauret, Kambiz Vafai, Suvash C. Saha, YuanTong Gu
      Tortuosity and porosity are critical parameters for characterizing fluid flow in porous media. These parameters are of paramount importance in the design of porous compact heat exchangers, packed bed reactors, and catalysis supports; however, in the context of heat exchangers, these parameters are generally formulated for single-phase fluid flow under steady-state conditions. However, most industrial flows in a porous medium such as metal foams comprise of transient particle-laden fluid flow. A coupled finite volume and discrete element method (FVM-DEM) is developed to examine transient particle-laden Stokesian flow, particulate fouling (deposition), and fluid flow patterns in an idealized porous metal foam. This work presents a comparative analysis of the analytical and numerical pressure drop profiles. The solid-gas suspension in a porous media is discussed. Secondly, a new time-dependent pore-level fluid tortuosity relation is established which is linked with a modified porosity-based Darcy-Forchheimer equation. Fluid disturbance attributable to the inception of particle deposition is quantified by the tortuosity and instantaneous shift in streamline angle ratio. It is shown that the streamline angle ratio and the meandering of fluid flow paths vary with changing porosity and tortuosity. Moreover, the Reynolds number and particle density play a critical role in the alteration of the resistance to fluid flow and permeability which is related to the tortuosity and variation in fluid flow behaviour. The results and numerical method serves as a steppingstone to better optimize various heat exchangers while taking into account complex multiphase flow behaviour and the tortuous flow paths of porous structures.

      PubDate: 2017-07-22T22:07:17Z
       
  • Roles of hydrogen sulfide concentration and fuel gas injection on
           aromatics emission from Claus furnace
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Salisu Ibrahim, Ramees K. Rahman, Abhijeet Raj
      Acid gas (H2S and CO2) recovered from sour feedstocks is treated in Sulfur recovery units (SRU) to obtain sulfur. The frequent changes in acid gas composition often result in lean acid gas, containing higher volume of CO2 than H2S. Lean acid gas causes flame instability that result in inefficient destruction of feed impurities in Claus furnace. To mitigate this problem, fuel gas (with >90% CH4) is co-fired with acid gas to increase furnace temperature and prevent flame extinction. The addition of fuel gas in Claus furnace may aggravate the production of polycyclic aromatics hydrocarbons (that cause frequent catalyst deactivation), and CS2 and COS (that reduce sulfur yield). Clearly, the amount of fuel gas injected into Claus furnace needs to be optimized. The previous optimization studies have given less importance to the roles of H2S concentrations in acid gas and the injected fuel gas on the production of aromatics and organosulfur species. This paper explores the fate of undesired aromatics, COS and CS2 in the Claus furnace over a wide range of H2S concentrations in acid gas using a detailed reaction mechanism. Experimental data on species concentration from a SRU is presented, and is used for mechanism validation. The effect of fuel gas co-firing with typical Claus feed containing 30–50% H2S is presented alongside detailed analysis of species compositions in the thermal section. An increase in fuel gas flow rate (from 0 to 200kmol/h) increased aromatics production in the furnace for lean acid gases. For rich acid gas, a decrease in aromatics production occurred as fuel gas flow rates was increased. The divergent trends were found to be occurring due to the reduced reactivity of methane in comparison to H2S at low flame temperatures, the dilution effect of unburnt CH4, CO2, and N2 in the furnace, and the endothermic hydrocarbon pyrolysis reactions leading to aromatics formation and growth. Fuel gas addition also led to COS and CS2 formation to reduce sulfur yield. The results indicate that fuel gas may not be the best solution for aromatics destruction in the Claus process for lean acid gas feeds.

      PubDate: 2017-07-22T22:07:17Z
       
  • Complete removal of carbon monoxide by functional nanoparticles for
           hydrogen fuel cell application
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Hanseul Choi, Joonwoo Kim, Suk-Jin Choung, Jinsoo Kim, Mohd Roslee Othman
      A bi-functional catalyst containing a stable cubic cerium-zirconium oxide phase was prepared and used for CO preferential oxidation. Pure ceria was observed to achieve the highest CO conversion of over 95% at >300°C. A bi-functional ceria-zirconia successfully reduced the reaction temperature to 200°C but at the expense of lower conversion of 85%. The bi-functional catalyst containing copper species at 5wt% of the metal precursor demonstrated the ability to oxidize CO completely at 115°C. This was made possible by the high oxygen storage capacity (OSC) of the catalyst which was measured to be 707.7μmolO2/g.

      PubDate: 2017-07-22T22:07:17Z
       
  • Optimizing sulfur-driven mixotrophic denitrification process: System
           performance and nitrous oxide emission
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Yiwen Liu, Huu Hao Ngo, Wenshan Guo, Junliang Zhou, Lai Peng, Dongbo Wang, Xueming Chen, Jing Sun, Bing-Jie Ni
      Nitrate contamination of groundwater has been recognized as a significant environmental problem world widely. Sulfur-driven mixotrophic denitrification has been demonstrated as a promising groundwater treatment process, which though plays an important role in nitrous oxide (N2O) emissions, significantly contributing to the overall carbon footprint of the system. However, the current process optimizations only focus on nitrate removal and excess sulfate control, with the N2O emission being ignored. In this work, an integrated mathematical model was proposed to evaluate the N2O emission as well as the excess sulfate production and carbon source utilization in sulfur-driven mixotrophic denitrification process. In this model, autotrophic and heterotrophic denitrifiers use their corresponding electron donors (sulfur and organic matter, respectively) to reduce nitrate to nitrogen gas, with each modeled as three-step denitrification (NO3 − to N2 via NO2 − and N2O) driven by sulfur or organic matter to describe all potential N2O accumulation steps. The developed model, employing model parameters previously reported in literature, was successfully validated using N2O and sulfate data from two mixotrophic denitrification systems with different initial conditions. Modeling results revealed substantial N2O accumulation due to the relatively low autotrophic N2O reduction activity as compared to heterotrophic N2O reduction activity, explaining the observation that higher carbon source addition resulted in lower N2O accumulation in sulfur-driven mixotrophic denitrifying system. Based on the validated model, optimizations of the overall system performance were carried out. Application of the model to simulate long-term operations of sulfur-driven mixotrophic denitrification process indicates that longer sludge retention time reduces N2O emission due to better retention of active biomass. High-level total nitrogen removal with significant N2O emission mitigation, appropriate excess sulfate control and maximized COD utilization can be achieved simultaneously through controlling the influent nitrate and COD concentrations.

      PubDate: 2017-07-10T02:45:56Z
       
  • On the effect of dispersed phase viscosity and mean residence time on the
           droplet size distribution for high-shear mixers.
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Sergio Carrillo De Hert, Thomas L. Rodgers
      Properties of emulsified product such as stability, rheology and interfacial area dependent on their micro-structure, specially their mean droplet size and droplet size distribution. Mechanistic models in literature focus on predicting the maximum droplet diameter or Sauter mean diameter but not in their size distribution. The effect of viscosity (9.58–295mPas), mean residence time and stirring speed (50–150s−1) have been investigated using an in-line laboratory scale rotor-stator and dilute (negligible coalescence) coarse emulsions with seven Silicon Oils of different viscosity. Low viscous oils produced monomodal distributions whereas the ones for intermediate and high viscous oils were bimodal. The mode or modes of the distributions were used for the modelling of the large and small daughter droplet sizes. The droplet size modelling had a mean absolute error (MAE) of 8 % . To model the distributions by volume two Generalized Gamma functions were used and fitted using the least absolute error. The distributions were reasonably well-described while predicting the Sauter mean diameter of both mono and bimodal distributions with a MAE of 13.8 % .

      PubDate: 2017-07-10T02:45:56Z
       
  • Asymptotic limits on tablet coating variability based on cap-to-band
           thickness distributions: A discrete element model (DEM) study
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Chunlei Pei, James A. Elliott
      The uniformity of the coating thickness distribution is an important quality metric in the manufacture of pharmaceutical tablets during the spray coating process. An investigation of the asymptotic limits of coating thickness variability of tablets of different shapes was carried out based on their cap-to-band coating thickness distributions. A theoretical analysis shows that the cap-to-band coating thickness ratio is expected to be equal to the cap-to-band area ratio projected onto the spray direction divided by the actual cap-to-band surface area ratio. When the cap-to-band projected area ratio is larger (or smaller) than the cap-to-band surface area ratio, the mean coating thickness on the cap is larger (or smaller) than that on the band. To verify this, the dynamics of tablets in a rotating pan was modelled using discrete element method (DEM) simulations, while an image analysis technique based on the output of DEM simulations was applied to model the spray coating process and analyse the cap-to-band coating thickness ratio. A ray-tracing sampling method was further used to obtain the cap-to-band sample ratio. It was also found that a smaller spray angle with respect to the horizontal direction can decrease or even invert the cap-to-band coating thickness ratio, leading to a larger coating thickness on the band than the cap. Nevertheless, an asymptotic value of cap-to-band relative standard deviation can be reached once the cap-to-band coating thickness ratio becomes constant during the coating process. This asymptotic limit is within the range predicted based on the cap-to-band projected area ratio and surface area ratio.
      Graphical abstract image

      PubDate: 2017-07-10T02:45:56Z
       
  • Effects of different factors on sulfur trioxide formations in a coal-fired
           circulating fluidized bed boiler
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Baixiang Xiang, Wenfeng Shen, Man Zhang, Hairui Yang, Junfu Lu
      Experimental and numerical studies were conducted to determine the effects of different factors on homogeneous and heterogeneous formations of sulfur trioxide (SO3) in a coal-fired circulating fluidized bed (CFB) boiler. In the experiments, homogeneous and heterogeneous formations of SO3 under coal-fired CFB combustion conditions were measured using controlled condensation and S balance, respectively. Meanwhile, homogeneous SO3 formation under coal-fired CFB combustion conditions was numerically calculated using an improved SO2/O2/H2O/CO2/CO/NO kinetic mechanism. Measurement results showed that the effect of fly ash on SO3 concentration was slightly stronger than that of circulating ash. Both experimental and numerical results showed that SO3 concentration was apparently affected by SO2, O2, and H2O concentrations and temperature but barely affected by CO2 concentration.

      PubDate: 2017-07-10T02:45:56Z
       
  • Hydrogenation of 2-ethylanthraquinone with monolithic catalysts: An
           experimental and modeling study
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Yanyan Guo, Chengna Dai, Zhigang Lei
      A series of Pd/zeolite/cordierite (zeolite=MCM-41, SBA-15, Beta, or MCM-22; cordierite=COR) monolithic catalysts, as well as Pd/ZIF-8/COR, Pd/Al2O3/COR, and Pd/SiO2/COR, were prepared, characterized, and evaluated for the hydrogenation of 2-ethylanthraquinone (eAQ) to 2-ethyl-9,10-anthrahydroquinone (eAQH2). We found that a 0.8% Pd/MCM-41/COR catalyst exhibited the highest H2O2 yield (7.54gL−1) and selectivity (85.3%) toward active quinones for hydrogen peroxide (H2O2) production using the anthraquinone method. Notably, the Pd efficiency (1573gH2O2 g−1Pdh−1) for the 0.8% Pd/MCM-41/COR monolithic catalyst was much higher than that of a commercial pellet catalyst (500gH2O2 g−1 Pdh−1). The intrinsic kinetics of hydrogenation of eAQ over 0.8% Pd/MCM-41/COR was measured, and the kinetic equation parameters were incorporated into a computational fluid dynamics (CFD) model. The mass transfer coefficients for the monolithic catalysts are 5–20 times higher than the pelleted catalyst. In addition, we found that the gas-liquid mass transfer is the controlling step, showing the unique advantages of monolithic catalysts for process intensification.

      PubDate: 2017-07-10T02:45:56Z
       
  • Community-based synthesis of distributed control architectures for
           integrated process networks
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Sujit Suresh Jogwar, Prodromos Daoutidis
      In this paper, we propose a graph-theoretic framework for designing architectures for distributed control. Specifically, the popular concept of community structure is used to decompose an integrated network into multiple sub-networks with minimum interactions. The state space of the network is represented as an equation graph (directed). Communities identified on this graph represent sub-controllers for the distributed control system. A quality measure ‘interactivity’ is defined to compare such decompositions. The proposed method has many advantages (e.g. possibility of non-square controllers, provision to ensure controllability and observability, scalability, etc.) over existing approaches. The effectiveness of the proposed framework is illustrated via several industrially relevant examples.
      Graphical abstract image

      PubDate: 2017-07-10T02:45:56Z
       
  • Influence of recycle streams of C5/C6 and C4 hydrocarbon cuts on the
           performance of methanol to propylene (PVM) reactors
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Abolghasem Kazemi, Masoud Beheshti, Reza Khalili
      Conversion of methanol to propylene combined with cracking of C5/C6 and C4 hydrocarbon cuts was studied on a commercial Süd-Chemie Germany ZSM-5 catalyst. The C5/C6 hydrocarbon cut consisted of hydrocarbons with 5 and 6 carbons in their structure (27.74% i-pentene, 43.14% i-hexene, 3.70% i-pentane and 7.37% i-hexane). The C4 hydrocarbon cut consisted of both olefinic and paraffinic molecules. A fraction of the feed hydrocarbon mixture was converted to other hydrocarbons while the conversion of methanol was remained close to 100%. It was observed that co feeding of the hydrocarbons mixture with methanol considerably increase propylene selectivity. Propylene selectivity up to 61% was gained in the propylene via methanol (PVM) process by co feeding of C5/C6 hydrocarbon cuts. For the C4 hydrocarbon cut, propylene selectivity up to 65% was obtained. However, these values do not represent the actual selectivity at actual flow rates of recycle streams. Based on third order polynomials, effects of steady state recycle streams of these cuts are also predicted in this paper. At the best conditions of a steady state recycle stream, 47.7% selectivity was obtained for propylene in the PVM reactors.

      PubDate: 2017-07-10T02:45:56Z
       
  • Diffusion controlled LHHW kinetics. Simultaneous determination of chemical
           kinetic and equilibrium adsorption constants by using the Weisz-Prater
           approach
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Juan Rafael García, Claudia María Bidabehere, Ulises Sedran
      A method to simultaneously determine the chemical kinetics ( kC T ) and Langmuir’s adsorption equilibrium ( K L ) constants in porous catalyst particles where chemical reactions following Langmuir-Hinshelwood-Hougen-Watson (LHHW) kinetics (first order on the concentration of the adsorbed species) proceed under the existence of diffusion mass transfer limitations was proposed. Two parameters characterize this steady state diffusion-adsorption-reaction system: the well known Thiele modulus ϕ and the dimensionless adsorption equilibrium constant K , which is defined as the product between K L and the fluid phase concentration of the reactant ( C f ) . It was shown that the non-linear adsorption equilibrium is the reason that, given ϕ , the larger the K , the flatter the concentration profile and, consequently, the volume average chemical reaction rate and the effectiveness factor are higher. Although the Weisz-Prater (W-P) criterion has been previously extended to non-linear kinetics to evaluate the relative magnitude of diffusion limitations inside porous catalyst particles, this method allows determining the kinetic and adsorption parameters by using the W-P parameter, as assessed from a few laboratory experiments. Differently from the classical W-P criterion (first order kinetics), a single value of W-P parameter below which the chemical control could be secured does not exist for LHHW kinetics. Those “limit” values depend on K and increase with it. The fact that ϕ is independent from C f , while K certainly depends on it, makes it easier to simultaneously determine K L and kC T under reaction conditions. When K is small (e.g., lower than 0.1), the model converges to the solutions typical in textbooks, where linear adsorption equilibrium is taken into account, which under steady state conditions only allow estimating the kC T K L product, but not the individual constants.

      PubDate: 2017-07-10T02:45:56Z
       
  • First, second and nth order autocatalytic kinetics in continuous and
           discontinuous reactors
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Vincenzo Russo, Tapio Salmi, Frank Mammitzsch, Olatunde Jogunola, Rüdiger Lange, Johan Wärnå, Jyri-Pekka Mikkola
      Autocatalytic phenomena in chemical kinetics originate from various reasons, such as acid-catalytic effects of reaction products or change of the physical properties of the reaction mixture. The impact of autocatalytic kinetics on the chemical reactor design is crucially important leading to deviations from standard design rules. The impact of autocatalytic effects on first, second and nth order kinetics was investigated for batch, plug flow, backmixed, axial dispersion and recycled plug flow reactors was analyzed by classical approach and numerical simulations. Efficient numerical strategies were developed for the different reactor models. The results showed how an optimal degree of backmixing (Péclet number) and optimal recycle ratio can be determined for tubular reactors and how the reactor volume can be minimized for specific cases. Generic examples as well as hydrolysis of alkyl formate were considered as case studies.
      Graphical abstract image

      PubDate: 2017-07-10T02:45:56Z
       
  • Dynamics of bubble formation in highly viscous liquids in a flow-focusing
           device
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Chong Zhang, Taotao Fu, Chunying Zhu, Shaokun Jiang, Youguang Ma, Huai Z. Li
      This article reports the dynamics and mechanism for N2 bubble formation in highly viscous glycerol-water mixtures in a flow-focusing device by using a high-speed digital camera. The evolution of the volume for the gaseous thread during bubble formation is highlighted. A square microchannel with 400μm×400μm is used. The bubble formation process can be divided into an expansion stage and a breakup stage. The volume of the gaseous thread increases linearly with time in the two different stages, however, the growth rate in the breakup stage is always greater than that in the expansion stage. The growth rate for the evolution of the gaseous thread is controlled by the capillary number and the gas-liquid flow rate ratio, with varied exponents for the two stages. The turning point of the two stages occurs at the moment when the width of gaseous neck reaches its maximum, and the dimensionless time at the turning point is related to the gas-liquid flow rate ratio. Finally, the volume of generated bubbles in highly viscous liquids in the flow-focusing device is scaled with the capillary number and the gas-liquid flow rate ratio.
      Graphical abstract image

      PubDate: 2017-07-10T02:45:56Z
       
  • An entropy criterion for the validity of Navier-Stokes order continuum
           theory for gas-solid flow: Kinetic theory analysis
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Bidan Zhao, Jing Wang, Junwu Wang
      Navier-Stokes order continuum theory (NS theory) established on the basis of local thermodynamic equilibrium (LTE) postulate has been widely used to study gas-solid flows. Qualitatively, the postulate is valid for systems sufficiently close to equilibrium, however, continuum theory provides no information on how small these deviations from equilibrium should be in order to guarantee the validity of LTE. To this end, kinetic theory analysis was carried out to formulate an entropy criterion, it was shown that (i) the entropy density up to the NS order is exactly the same as the one at the LTE condition, meaning that the LTE postulate is only valid for linear non-equilibrium regime, although NS theory and the LTE postulate are logically self-consistent; (ii) an entropy criterion characterizing the relative importance of nonlinear effects is derived, which should be small in order to make sure that the LTE postulate is valid and also sets the boundary of validity of NS theory; and (iii) the proposed entropy criterion, I s ≪ 1 , is not only a function of granular temperature gradient and velocity gradient, but also a function of 1 - e 2 characterizing the inelasticity of particle-particle collisions. It is more complex and systematic than the traditional criterion based on the Knudsen number, Kn ≪ 1 .

      PubDate: 2017-07-10T02:45:56Z
       
  • A recurrence CFD study of heat transfer in a fluidized bed
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): T. Lichtenegger, E.A.J.F. Peters, J.A.M. Kuipers, S. Pirker
      Significant progress in modeling and simulation techniques has opened the door to accurate descriptions of highly dynamic gas-solid flows. However, such investigations are limited to short durations by enormous computational costs, making long-term numerical experiments on slow processes like heat transfer unfeasible. We employ the potentially groundbreaking new approach recurrence CFD to decouple fast, recurrent dynamics from slower degrees of freedom. This allows us to study heat transfer in lab-scale fluidized beds consisting of about 57000 and 95000 particles ( T p , 0 = 90 ° C, T gas , in = 20 ° C ), respectively, at 1/300 of the runtime of conventional CFD-DEM simulations on the same hardware with hardly distinguishable evolutions of particle mean temperatures even after 60 s process time. A detailed performance analysis reveals possible future improvements on the way to industrial-size systems.

      PubDate: 2017-07-10T02:45:56Z
       
  • An efficient level set remedy approach for simulations of two-phase flow
           based on sigmoid function
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Min Chai, Kun Luo, Changxiao Shao, Jianren Fan
      The current work presents an improved, concise and inexpensive remedy approach for level set methods to deal with the mass non-conservation issue especially in large-scale simulations, where computational cost is always a constraint limiting broad applications. In this work, a sigmoid function originated from the work of Olsson and Kreiss (2005) is further utilized to describe the local relationship between the signed distance function of level set method and the liquid volume fraction. An improved criterion on determining the correction within relevant cells is introduced. And the upwind scheme for curvature calculation is implemented to handle small and/or thin structures. Several benchmark validations and gas-liquid flow problems are carried out to assess the approach. The main advantage of this approach is that the additional CPU cost for multiphase solver caused by remedy procedure, when relative to that without remedy, can be greatly reduced from about 100% to less than 10%, making it suitable for large-scale simulations. This approach also gains a higher accuracy in predicting the interface location while inherits the good performance of the previous method on ensuring mass conservation. Analyses prove that the level set remedy approach is suitable and reliable in simulating two-phase flows.

      PubDate: 2017-07-10T02:45:56Z
       
  • Multi-scale modelling of heat transfer in polyurethane foams
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Pavel Ferkl, Miloš Toulec, Erik Laurini, Sabrina Pricl, Maurizio Fermeglia, Stefan Auffarth, Berend Eling, Volker Settels, Juraj Kosek
      The influence of morphology and cell gas composition on heat insulation properties of polyurethane (PU) foams was investigated using a multi-scale mathematical model. The polymer absorption coefficient was determined from quantum chemical computations. Reverse non-equilibrium molecular dynamics was used to calculate the thermal conductivity of polymer and gas mixtures relevant to PU foams. The equivalent foam conductivity was calculated using homogeneous phase approach. The individual models were coupled together using suitable surrogate models within MoDeNa framework. To validate the proposed model 9 foam samples were prepared using different recipes, their morphology was characterized and their thermal conductivity was measured. The difference between experimental and predicted values was comparable to experimental error. Developed multi-scale model was used to identify the most suitable relation for the calculation of thermal conductivity of gas mixtures in PU foams and to quantify the influence of foam density, cell size, and strut content on heat insulation properties of PU foams.
      Graphical abstract image

      PubDate: 2017-07-10T02:45:56Z
       
  • Study of the effect of condensation and evaporation of water on heat and
           mass transfer in CO2 absorption column
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Koteswara Rao Putta, Hallvard F. Svendsen, Hanna K. Knuutila
      A rate-based combined heat and mass transfer model developed based on penetration theory is used to study the effect of water evaporation and condensation on the CO2 absorption process using six different cases with real pilot-scale plants flue gas conditions. The effect of water evaporation and condensation on the concentrations, temperature profiles and reaction rates are studied in detail. The model predicted reasonable profiles as one would expect for water condensation and evaporation. The degree of liquid temperature rise depends mainly on the gas water saturation level and the temperature difference between the gas and liquid. Temperature profiles are flat in the liquid, whereas the transferring components create steep concentration gradients close to the interface making the interface concentrations change rapidly with position in absorber. This is in line with the thermal and mass diffusivities. Concentration build-up or depletion of species takes place in the liquid phase close to the gas-liquid interface up to 10μm distance from the interface. For the case with absorber bottom pinch conditions, it was found that the CO2 flux sign changes and desorption occurred when taking the evaporation and condensation effects into account, whereas, without these effects, only absorption was predicted. For most of the cases, absorption rate of CO2 was not affected significantly even though concentration gradients and temperature changes were found. However, for the extreme case of warm unsaturated exhaust from an NG fired plant, case C1, and for the near pinch situation, case C6, significant changes to the CO2 absorption rates were found.

      PubDate: 2017-07-10T02:45:56Z
       
  • On the internal solids circulation rates in freely-bubbling gas-solid
           fluidized beds
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): J.A. Medrano, M. Tasdemir, F. Gallucci, M. van Sint Annaland
      The solids mass flux distribution and internal solids circulation rates in freely-bubbling gas-solid fluidized beds has been studied in detail in a pseudo-2D column. A non-invasive Particle Image Velocimetry (PIV) combined with Digital Image Analysis (DIA) technique has been further extended to investigate and quantify the gas and solids phase properties simultaneously for different particle types and sizes (all Geldart B type) at different fluidization velocities. It is found that the solids fluxes increase strongly, practically linearly, as a function of the vertical position and depend on the excess gas velocity but not on the particle size, while the most often used phenomenological two-phase fluidized bed models assume the vertical solids fluxes to be constant. To further investigate this important discrepancy, the underlying assumptions of the phenomenological models have been validated, especially concerning the average solids fraction inside the bubbles, the laterally and time-averaged axial bubble fraction profile (or visual bubble flow rate) and the wake parameter (the amount of solids carried along a bubble relative to the bubble volume). To this end, the PIV/DIA technique was further extended and a new method for the determination of the wake parameter is proposed. From the experimental results, it was concluded that i) the average solids fraction inside the bubbles is about 2.5–3% for glass beads and alumina particles and is practically independent of the excess gas velocity and particle size; ii) the measured laterally and time-averaged bubble fractions are considerably lower compared to often used correlations from literature, which would lead to a significant over-prediction of the visual bubble flow rate and iii) the wake parameter depends strongly on the bubble size and with the developed correlation the axial solids mass fluxes as a function of the vertical position can be well described. Finally, the influence of these findings was evaluated by performing a sensitivity analysis with an existing phenomenological model for fluidized beds with the new values and closures considering the case of the heterogeneously catalyzed steam methane reforming. With the developed findings and correlations the predictions with the two-phase phenomenological models can be further improved, especially concerning the hydrodynamics of the solids phase.
      Graphical abstract image

      PubDate: 2017-07-10T02:45:56Z
       
  • A model for diffusion of water into a swelling particle with a free
           boundary: Application to a super absorbent polymer particle
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): T. Sweijen, C.J. van Duijn, S.M. Hassanizadeh
      In this work, a model is developed for describing the swelling of an individual particle, made of Super Absorbent Polymers (SAP). Governing equations for the water uptake at the particle surface, diffusion of water into the particle and the subsequent swelling of the particle are developed for an irregularly shaped particle. The modelling domain is assumed to have a free and moving boundary, thus a moving particle surface, to account for the increase in particle size. In addition, the entrance of water through the particle surface is modelled as a first-order kinetic process. The proposed model is then simplified for a spherical particle, made dimensionless, projected onto a fixed grid, and solved using an explicit numerical scheme. A dimensionless number is defined as the ratio of kinetics of water uptake at the particle surface to the water diffusivity. Using this dimensionless number, three regimes of swelling kinetics can be identified: (i) diffusion is limiting, (ii) water uptake is limiting, or (iii) both processes are limiting. Numerical results indicate that experimental data from literature can be reproduced when assuming water uptake kinetics at the particle surface to be very fast; i.e. instantaneous, thus diffusion being the controlling mechanism. Of course, for SAP particles having a different composition, the particle surface may slow down the swelling kinetics. Our model is compared to three other models found in the literature. They all give a similar result but with different diffusive coefficients.

      PubDate: 2017-07-10T02:45:56Z
       
  • A novel simplified multivariate PBE solution method for mass transfer
           problems
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): A. Buffo, V. Alopaeus
      Interphase mass transfer estimation may require not only the accurate knowledge of the interfacial area, which depends on the information about the size of each dispersed element, but also on the driving force, that can be different if the elements of the disperse phase have different chemical composition. To take into account such polydispersity, bivariate (or multivariate) population balance model (PBM) are formulated according to physical phenomena occurring in the investigated mass transfer problem. This often includes aggregation, breakage, advection, mass transfer of the chemical species and chemical reactions of the transferring components. In this work we propose a novel and simplified method to solve the bivariate/multivariate population balance equation for a mass transfer problem, based on the high-order moment-conserving method of classes (HMMC) (Alopaeus et al., 2006). The proposed method is based on the idea of deriving additional material balance equations for the concentration of the droplets belonging to each size class, reducing significantly the total number of unknown variables with respect to true bivariate/multivariate method of classes. This modeling approach is compared with two other possible solution methods for a test case in which mass transfer and chemical reactions occur in a system with two immiscible liquid phases. In the first the traditional approach is used, where a single material balance is formulated for the disperse phase along with PBM, while in the second a true bivariate/multivariate solution method is used. The results of this comparison show that the proposed method is robust and accurate, capable of properly describing the multidimensional droplet size-composition distribution needed to evaluate the mass transfer rates, in a fraction of the computational time compared with more accurate methods.

      PubDate: 2017-07-10T02:45:56Z
       
  • From core-shell to Janus: Microfluidic preparation and morphology
           transition of Gas/Oil/Water emulsions
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Shao-Bin Zhang, Xue-Hui Ge, Yu-Hao Geng, Guang-Sheng Luo, Jian Chen, Jian-Hong Xu
      In this article, gas-liquid-liquid emulsion drops were firstly generated by one-step method in a coaxial microfluidic device. Based on that, the effects of several parameters on the morphology transition from core-shell to Janus droplets was studied systematically. By tuning flow rates, interfacial tensions and viscosity, we can change the size and morphology of droplets. Furthermore, non-spherical microparticles were obtained by using photo-responsive reagent through solidification. The developed approach offers a novel and simple strategy on the synthesis of Janus emulsions and anisotropic microparticles with controlled morphologies.

      PubDate: 2017-06-28T20:33:12Z
       
  • DEM numerical investigation of wet particle flow behaviors in
           multiple-spout fluidized beds
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Tianqi Tang, Yurong He, Tong Tai, Dongsheng Wen
      Spout fluidized beds are important for industrial processing, and multiple-spout fluidized beds play an important role in chemical reactions. However, particle flow behaviors in multiple-spout fluidized beds are not well known in wet particle systems. In this study, the flow behaviors of particles were investigated in dry and humid multiple-spout fluidized beds using a discrete element method (DEM). The simulated spout fluidized beds are similar to the ones used in the Buijtenen et al.’s experiment (published in Chemical Engineering Science, 2011, 66(11): 2368–2376). In the reference, particle flow behaviors were measured and investigated by PIV and PEPT in multiple spout fluidized beds. In this work, the simulated results are compared with the experimental data in single and double spout fluidized beds from Buijtenen et al., and the time-averaged particle velocities are compared to validate the simulation method. In contrast, simulated results with a liquid content of 1% in the bed showed good agreement with the data in the experimental results with an air relative humidity of 50%. Different liquid contents of the particles were applied to investigate the particle flow behaviors in wet granular systems. The liquid bridge force had a strong influence on the flow behaviors of the particles in the dense region, which resulted in different hydrodynamic characteristics between the dry and wet particles. In addition, the drag force dominated the particle flow behavior in the dry and wet particle systems. Moreover, in a wet granular system, the mass particle fluxes decreased, and the fluctuation of the pressure drops increased with an increasing influence of the liquid bridge force on the particles. Furthermore, with an increasing liquid content, the energy fluctuation of the particles weakened gradually with less active motions. A comparison of the hydrodynamic flow behaviors in single-spout and double-spout fluidized beds was carried out as well. Comparisons of the solid circulation rate and the colliding characteristics between single-spout and double-spout fluidized beds were conducted. Particularly, a comparison of the mixing characteristics demonstrated that the particles were mixed more completely in a double-spout fluidized bed. Therefore, the double-spout fluidized bed could provide more adequate space for mass and heat transfer under the same condition. This was important in providing a theory for designing the industrial reactor.

      PubDate: 2017-06-28T20:33:12Z
       
  • Scale-up agitation criteria for Trichoderma reesei fermentation
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Nicolas Hardy, Frédéric Augier, Alvin W. Nienow, Catherine Béal, Fadhel Ben Chaabane
      Scale-up of aerobic fungal fermentation processes still remains a challenging issue for the biotechnology industry. This difficulty arises due to the complex interactions between operating conditions (agitation, aeration, etc.), the physicochemical state of the broth (viscosity, the dissolved oxygen concentration, etc.) and the biology of fungi (growth, production, morphology, etc.). Because of their size, filamentous fungi are affected by fluid dynamic stresses but quantification of this complex parameter is a difficult task. In general, indirect criteria are used for the effect of fluid dynamic stresses on scale-up (tip speed, power draw or the energy dissipation/circulation function (EDCF)). In order to better understand the impact of such criteria on the fermentation of the fungus Trichoderma reesei, a wide range of agitation conditions has been explored. The morphology of T. reesei fungus, its specific growth rate and the rheological properties of the broth have all been measured both at bench scale (∼2.5L) and for the first time, at a typical commercial scale. These three aspects of the fermentation at both scales were then compared with respect to tip speed, specific power and EDCF. This work has shown that tip speed as a correlator of any of these parameters is totally ineffective whilst the EDCF is clearly the best for extrapolating laboratory data to the commercial scale.

      PubDate: 2017-06-28T20:33:12Z
       
  • Numerical simulation and experimental study on a deoiling rotary
           hydrocyclone
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Long Huang, Songsheng Deng, Ming Chen, Jinfa Guan
      In this study, the internal flow field and oil-water separation performance of a rotary hydrocyclone (RH) were investigated using computational fluid dynamics (CFD) simulations and experimental methods. In the numerical simulation, the turbulence was modeled by Reynolds stress model; the oil-water two-phase flow was modeled using the Algebraic Slip Mixture model; and the rotating walls were modeled by Multiple Reference Frame method. The numerical results were consistent with the experimental results. The influences of pipe wall rotation speed and inlet flow rate were also investigated. The results demonstrate that both rotation speed and flow rate have significant impacts on the velocity profile; increasing rotation speed or decreasing flow rate decrease the pressure drop and increase separation efficiency. The presence of oil core was predicted by the numerical calculations and observed in the experiment. In conclusion, the results indicate that the newly designed RH is a separator with high efficiency and wide flow rate range.
      Graphical abstract image

      PubDate: 2017-06-28T20:33:12Z
       
  • Numerical investigation of entropy generation to predict irreversibilities
           in nanofluid flow within a microchannel: Effects of Brownian diffusion,
           shear rate and viscosity gradient
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Saeed Heshmatian, Mehdi Bahiraei
      In the present contribution, irreversibilities caused by heat transfer and friction for the water-TiO2 nanofluid flow in a circular microchannel are investigated by evaluating entropy generation rates. The effects of viscosity gradient, non-uniform shear rate and Brownian diffusion on particle migration are taken into account in order to examine the effect of nanoparticle arrangement on entropy generation rates. The results show that nanoparticle migration alters concentration distribution and consequently, changes entropy generation rates. Nanoparticle migration increases concentration of the particles in central regions, and this migration is more noticeable for higher mean concentrations and larger particles. Thermal entropy generation rate intensifies with increasing wall heat flux and particle size while decreases with increasing concentration. Frictional entropy generation rate increases by concentration increment and decreases by particles enlargement, while it changes trivially by increasing wall heat flux. Frictional entropy generation rate is larger than thermal entropy generation rate in the microchannel under study and therefore, total entropy generation mostly stems from friction. Thus, total entropy generation rate decreases by particles enlargement, which is a positive result according to second law of thermodynamics. Eventually, a model for entropy generation rates is developed using the numerical data by means of Artificial Neural Network (ANN).

      PubDate: 2017-06-28T20:33:12Z
       
  • Interaction of a spherical particle with a neutrally buoyant immiscible
           droplet in salt solution
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Ya Gao, Subhasish Mitra, Erica J. Wanless, Roberto Moreno-Atanasio, Geoffrey M. Evans
      The complex interactions of rigid spherical particles with interface (e.g., gas-liquid or liquid-liquid) underpin important industrial applications such as the separation of minerals using flotation method. The objective of the present work was to investigate this interaction process both experimentally and theoretically involving different size of particles (radius∼100–200μm) with varying surface wettability (contact angle∼50–70°) and a stationary neutrally buoyant immiscible oil-water interface (aniline droplet in salt solution) utilizing high speed imaging technique. The results showed that the particle size significantly affects the collision mechanism wherein collision with particle rebound was noted for larger size particles and collision without particle rebound was noted for the smaller size particles. Increasing surface hydrophobicity of the particles was found to be a governing factor that strongly attaches the particle to interface with immersion depth as high as ∼50% of particle radius. Collision polar angle was also noted to be a critical parameter that governs the attachment process. When collision polar angle was increased from 15° to 55°, attachment time was noted to increase by ∼2.5 times indicating decreasing probability of attachment. A discrete element model (DEM) was also developed to predict the interaction outcomes with suitable modification of the governing forces. To account for the effect of interface deformation, a spatially dependent capillary force profile was utilised incorporating the effect of interface deformation. The contact force model was modified to produce the collision with/without rebound outcomes. Also, the short range hydrodynamic drag force model was modified using suitable correction factors to account for the resistance in the intervening film between the approaching particle and the interface. Experimentally determined parameters such as droplet-particle separation distance, particle trajectory and velocity were compared with the DEM model predictions and reasonably good agreements were obtained.
      Graphical abstract image

      PubDate: 2017-06-28T20:33:12Z
       
  • Dynamic modeling of bubble growth in vapor-liquid phase change covering a
           wide range of superheats and pressures
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Qinggong Wang, Junping Gu, Zhouhang Li, Wei Yao
      Bubble growth in superheated liquid is a fundamental process in vapor-liquid phase change which occurs widely in thermal and chemical engineering. The strong coupling of heat, mass and momentum transfer at the interface brings difficulties to accurately predict the dynamics of bubble growth. At present, bubble growth under three extreme conditions, i.e. the very early growth stage, low superheats and low pressures, cannot be well described by traditional asymptotic solutions. In this work, a mathematical model was presented for better prediction of bubble growth in a superheated liquid. The model was derived from the equations of motion for a bubble and took account of the heat and mass balances at the interface. The model was validated with a series of experiments from the literature, covering a wide range of operating conditions. The newly proposed model can well predict the features of bubble growth at the very early stage (less than 10−6 s), for superheats varying from 0.8K to 36K and for system pressures reduced from 1.0atm to 0.0124atm. Analyses on the thermodynamics and hydrodynamics manifested that the bubble growth was characterized by three typical stages, i.e. a thermal delay stage, a fast expansion stage and a steady growth stage. The time lengths of these stages were related to the levels of superheat or system pressure. Characteristics of these stages were further discussed and the roles of interfacial forces under the different operating conditions were demonstrated.
      Graphical abstract image

      PubDate: 2017-06-28T20:33:12Z
       
  • CFD-DEM study of the effect of cyclone arrangements on the gas-solid flow
           dynamics in the full-loop circulating fluidized bed
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Shuai Wang, Kun Luo, Chenshu Hu, Jianren Fan
      Multiple cyclones are adopted to enlarge the capacity of circulating fluidized bed (CFB). In this work, the effect of cyclone arrangements on the gas-solid flow dynamics in the three-dimensional full-loop CFB is investigated by the computational fluid dynamics coupled with discrete element method (CFD-DEM). Flow patterns, pressure distribution, and non-uniform distribution of the gas-solid flow in the CFB is comprehensively studied. Results show that the CFB with multiple cyclones gives rise to some unique characteristics, including: (i) solid back-mixing behavior mainly occurs close to the front and back walls and in the four corners of the riser; (ii) the spiral directions of the internal and external vortexes of gas flow in the cyclone are same; (iii) the closed-loop pressure is obtained and the pressure drop in the standpipe and L-valve are nearly four times of that in the cyclone; (iv) gas-solid flow shows non-uniform distribution in the multiple cyclones, and the middle cyclones have higher solid holdup and solid velocity than the corner cyclones; (v) the axial symmetry arrangement for the multiple cyclones is better than the central symmetry arrangement in terms of the uniform distribution of solid flux in the cyclone and solid inventory in the standpipe. The results provide meaningful understanding for the design, scale-up, and optimization of CFB apparatuses.

      PubDate: 2017-06-28T20:33:12Z
       
  • Semi-analytical solutions for tubular chemical reactors
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): D. Rodrigues, J. Billeter, D. Bonvin
      The one-dimensional tubular reactor model with advection and possibly axial diffusion is the classical model of distributed chemical reaction systems. This system is described by partial differential equations that depend on the time t and the spatial coordinate z. In this article, semi-analytical solutions to these partial differential equations are developed regardless of the complexity of their initial and boundary conditions and reaction kinetics. These semi-analytical solutions can be used to analyze the effect on the concentrations at the current coordinates z and t of (i) the initial and boundary conditions, and (ii) the reactions that took place at an earlier time. A case study illustrates the application of these results to tubular reactors for the two cases, without and with diffusion.

      PubDate: 2017-06-28T20:33:12Z
       
  • A scale-bridging model for ice particles melting in air
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Hemant Bansal, Sina Ghaemi, Petr Nikrityuk
      This work is devoted to the development of a zero-dimensional semi-empirical sub-grid model (or submodel) which predicts the size and temperature of a solid particle undergoing a phase change inside a gaseous phase. Specifically, two sub-grid models are developed, one for a solid spherical particle and another for a solid cylindrical particle. The models can be implemented as a sub-grid model in Euler-Lagrange numerical models for particulate flows with solid particles undergoing phase changes. They can be used as scale-bridge relations to create a bridge between the scales in Euler-Lagrange models, to relate the heat transfer occurring at the interfacial scale to the macro heat transfer conservation equation written for the gaseous phase. The input parameters in our model are the particulate Reynolds number (Re), the Grashof number (Gr), the Stefan number (Ste) and the Prandtl number (Pr). The model has been validated against experimental results obtained by authors and existing experimental results produced by Janna and Jakubowski (1990). Good agreement is observed between our model predictions and both experimental results. The importance of a thin water film around the melting ice particle is discussed. The emissivity of the water film has been found to be influential in determining the melting rate of the ice particle.

      PubDate: 2017-06-28T20:33:12Z
       
  • Mean stop paths and diffusion regimes of molecules in one-dimensional
           zeolite channels
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Jichang Liu, Zhenfei Cheng, James Wei, Qiancheng Zhang, Xiang Chen, Yuhao Cen, Linfeng Li
      Molecular dynamics methods were used to simulate the diffusion of noble gas molecules, Ne, Ar, and Kr, in the one-dimensional zeolite channels of VET, AFI, VFI, and MCM-41. The gaseous, Knudsen, and configurational diffusion regimes were concisely described by a diffusion regime map. The boundary between the gaseous and the Knudsen diffusion regimes was determined by the probability, Pmm, of bimolecular collision, which was a function of both diameter ratio (dc/dm ) and volume density ρV . For a molecule in a channel surrounded by other molecules, the concept of mean stop path (MSP) was proposed as the average distance between collisions, either with another molecule or with the channel wall. The MSP depends on both the mean free path and the difference in channel and molecular diameters (dc -dm ). A theoretical model for calculating MSP of noble gas molecules in one-dimensional zeolite channels was derived based on the additivity of diffusion resistances. The mean stop path can describe the characteristics of molecular motion in a zeolite channel in the same way that mean free path does in an infinite space.
      Graphical abstract image

      PubDate: 2017-06-28T20:33:12Z
       
  • Investigating the effects of hydrodynamics and mixing on mass transfer
           through the free-surface in stirred tank bioreactors
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Anne de Lamotte, Angélique Delafosse, Sébastien Calvo, Frank Delvigne, Dominique Toye
      In stirred-tank bioreactors, flow structures of various length and time scales are implied in scalar transport phenomena, such as gas species transfer through the liquid free-surface and their homogenization in the bulk. A proper understanding of the underlying mechanisms, i.e. hydrodynamics, mixing and mass transfer, and of their interactions is required to design and develop reliable and efficient production-scale bioprocesses. The objective of the present work is to experimentally investigate the coupling between gas-liquid mass transfer of oxygen with mixing efficiency and circulation patterns inside an arbitrarily chosen stirred-tank configuration aerated through the liquid free-surface, a baffled 20L-vessel agitated by two Rushton turbines. Based on global parameter values, the most appropriate rotating speed, N =300rpm, is selected in order to further study local hydrodynamic quantities using Particle Image Velocimetry (PIV), as well as mixing and mass transfer dynamics using Planar Laser-Induced Fluorescence (PLIF). The results obtained with these local experimental methods are analyzed in detail. Their averages are first successfully compared to global data. Statistical analysis of their spatial distributions show that large-scale flow patterns significantly influence mass transfer through the free-surface of the stirred tank. Even if global measurements show that global characteristic times for mixing and mass transfer differ by two orders of magnitude, local experimental characterization shows persistent vertical gradients of dissolved gas concentrations. So the dissolved gas concentration is not as perfectly uniform as one might expect.

      PubDate: 2017-06-28T20:33:12Z
       
  • Numerical modelling and analysis of reactive flow and wormhole formation
           in fractured carbonate rocks
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Piyang Liu, Jun Yao, Gary Douglas Couples, Zhaoqin Huang, Hai Sun, Jingsheng Ma
      Combining the two-scale continuum model and the discrete fracture network model, a continuum-based model is developed that calculates the reactive flow of acid in carbonate rock with a complex fracture network. The locations of fractures in the model are explicitly defined and the method can capture complex geometric relationships. The governing equations are discretized by the finite-volume method, where the diffusion term and convection term are discretized using the two-point flux approximation (TPFA) scheme and the upwind scheme, respectively. The physical domain is discretized by Delaunay triangulation. To keep the robustness and efficiency of the TPFA scheme, the optimization algorithm is used to move the centroid node of the control volume to improve the orthogonality of the grids. Numerical simulations of reactive flow in 2D fractured porous media, in cases with simple and complex fracture arrays, under linear and radial flow conditions, are presented. In particular, a sensitivity analysis of the dissolution process with respect to the presence of fractures, fracture aperture, fracture distribution, and acid injection rate, is conducted.

      PubDate: 2017-06-28T20:33:12Z
       
  • Characteristics of liquid flow in a rotating packed bed for CO2 capture: A
           CFD analysis
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Peng Xie, Xuesong Lu, Xin Yang, Derek Ingham, Lin Ma, Mohamed Pourkashanian
      Rotating packed beds (RPBs) have been proposed as an emerging technology to be used for post-combustion CO2 capture (PCC) from the flue gas. However, due to the complex structure of the packing in RPBs, characteristics of the liquid flow within RPBs are very difficult to be fully investigated by experimental methods. Therefore, in this paper, a two-dimensional (2D) CFD model has been built for analysing the characteristics of liquid flow within an RPB. The volume of fluid (VOF) multiphase flow model is implemented to calculate the flow field and capture the interface between the gas and liquid phases in the RPB. The simulation results show good agreement with the experimental data. The distinct liquid flow patterns in different regions of an RPB are clearly observed. The simulation results indicate that increasing the rotational speed dramatically decreases the liquid holdup and increases the degree of the liquid dispersion. The increasing liquid jet velocity decreases the liquid residence time but slightly increases the liquid holdup. In addition, the liquid holdup increases and the degree of the liquid dispersion decreases with increasing MEA concentration, but the effects are weaker at a higher rotational speed. With the increasing of the contact angle, both the liquid holdup and the degree of the liquid dispersion are reduced. This proposed model leads to a much better understanding of the liquid flow characteristics within RPBs.

      PubDate: 2017-06-28T20:33:12Z
       
  • A complex model for the permeability and porosity of porous media
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Xiao-Hua Tan, Li Jiang, Xiao-Ping Li, Yue-Yang Li, Kai Zhang
      Transport phenomenon in porous media is essential in various scientific and engineering fields. The permeability and porosity of porous media serve important functions in transport phenomena. In this study, a complex model that considers the characters of pore microstructure and fluid in porous media is developed for the permeability and porosity of porous media. The flow rate expressions of this model are compared with those of previous models. As the proposed models relate the properties of fluids to the structural parameters of porous media, the various expressions of the developed model can reveal the phenomena of all types of fluid flow in a variety of porous media. The predicted permeabilities and porosities show good agreement with the available experimental data and illustrate that the proposed model can be used to characterize flow in porous media.

      PubDate: 2017-06-28T20:33:12Z
       
  • Numerical study of liquid-liquid mixing in helical pipes
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): M. Mansour, Z. Liu, G. Janiga, K.D.P. Nigam, K. Sundmacher, D. Thévenin, K. Zähringer
      The flow characteristics and the mixing performance of two miscible liquids in helical pipes have been studied numerically by computational fluid dynamics (CFD). The scalar transport technique is employed to quantify species mixing between the two fluids. The focus of the present study is set on investigating the optimal mixing behavior as a function of different parameters. The study is carried out for a wide range of relevant Schmidt and Reynolds numbers for laminar flow conditions. The Reynolds number (Re) and Schmidt number (Sc) have been varied from 5 to 104, and from 10 to 105, respectively. The model is first validated against experimental data from the literature. The effect of the inlet configuration is then examined; a vertical liquid interface at the inlet lead to the highest mixing efficiency. For low values of the Reynolds number, the results show that the mixing efficiency is reduced with increasing Schmidt number, until an asymptotic behavior is reached for very high Sc. For high values of the Reynolds number, increasing Schmidt number is observed to have only a minor influence on the mixing coefficient. The Reynolds number is found to have a more complex impact on mixing efficiency. Nevertheless, two optimal values of the Reynolds number can be found that lead to best mixing conditions in the laminar regime for a given length of the helical pipe. Though both values depend on the available length of the helix, they are typically found around Re≈50 and Re≈1000.
      Graphical abstract image

      PubDate: 2017-06-28T20:33:12Z
       
  • Controlling the specific growth rate via biomass trend regulation in
           filamentous fungi bioprocesses
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Daniela Ehgartner, Thomas Hartmann, Sarah Heinzl, Manuela Frank, Lukas Veiter, Julian Kager, Christoph Herwig, Jens Fricke
      Increasing pressure on product quality and quantity pushes solutions of process control to be a central issue in pharmaceutical bioprocesses. Especially online biomass estimation, and further control of the specific growth rate are of central importance because they describe the catalyst of the reaction. For penicillin producing bioprocesses with filamentous microorganisms, this was underlined by recent findings describing the influence of the specific growth rate on the specific production rate. Hence, the specific growth rate needs to be controlled on a certain level to achieve high productivity. In this study, we developed a control strategy for the specific growth rate based on online estimation of viable biomass via dielectric spectroscopy. The method was verified using an at-line staining method for viability measurement. The online viable biomass estimation is applicable in the growth and decline phase, coping with physiological and morphological changes of filamentous fungi. Furthermore, the control strategy adapts to changing biomass yields, which is a big issue in the bioprocess for penicillin production applied in this study. Two application runs were conducted, yielding in proper online viable biomass estimation and control of the specific growth rate at a constant level of 0.012h−1. We achieved biomass predictions with an average error of 1.5g/l over the whole fed-batch process. In the decline phase, the control of specific growth rates was not possible due to physiological constrains. However, in the growth phase, a total specific growth rate of 0.013h−1 was achieved, which met the pre-defined acceptance criterion for this method. The method is thus ready for viable biomass estimation in the growth and in the decline phase of the penicillin production process. Furthermore, the method is applicable to control the specific growth rate during the growth phase.
      Graphical abstract image

      PubDate: 2017-06-20T14:51:28Z
       
  • Heat transfer to a gas from densely packed beds of cylindrical particles
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Arpit Singhal, Schalk Cloete, Stefan Radl, Rosa Quinta-Ferreira, Shahriar Amini
      Particle resolved direct numerical simulation (PR-DNS) has been used extensively to obtain closures for heat transfer from static particle arrays. However, most of the currently available closure models are valid for packings of spherical particles only. We present closure models for momentum and heat transfer in densely packed cylindrical particle assemblies of different aspect ratios (2, 4 and 6). Our packings are generated using the Discrete Element Method (DEM). Subsequently, the void space is meshed with a high quality computational grid, and steady-state DNS simulations are completed to provide insight into the local heat transfer and pressure drop characteristics. The variation observed in the values for the local heat transfer rates from our PR-DNS study implies the necessity of specifying confidence intervals when reporting a correlation for the corresponding Nusselt number. Our newly developed correlations are applicable to densely packed beds of cylindrical particles in the porosity range (0.405<ε<0.539), and allow the estimation of the variability of the Nusselt number.
      Graphical abstract image

      PubDate: 2017-06-20T14:51:28Z
       
  • Thermal analysis of high frequency electromagnetic heating of lossy porous
           media
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): Asghar Sadeghi, Hassan Hassanzadeh, Thomas G. Harding
      Industrial applications of the electromagnetic wave as a source of energy have been increasing in recent years. One of the growing areas of application of electromagnetic heating (EMH), especially using high frequency waves, is the heating of geological media for extraction of hydrocarbons. In this work, electromagnetic field propagation in a lossy, electrically isotropic, and homogenous medium was studied to determine the effectiveness of EMH for heavy oil recovery. The electromagnetic heat source is modeled using Beer-Lambert’s law coupled with heat conduction. New analytical solutions are developed to find temperature distribution in linear and radial geometries subject to various boundary conditions. The effect of electromagnetic heat generation on thermal penetration depth is examined. One of the challenges in electromagnetic heating of geomaterials has been reflection of the incident wave due to impedance mismatch and thus loss of the applied power. The analytical solutions developed allow determination of absorbed power by the geological media and thus can be used as a tool to predict efficiency of electromagnetic heating. In addition, the aforementioned solutions can be used as forward model for design of experiments and to estimate the electromagnetic absorption coefficient of geomaterials.

      PubDate: 2017-06-20T14:51:28Z
       
  • Anaerobic degradation of 2-propanol: Laboratory and pilot-scale studies
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): N. Vermorel, P. San-Valero, M. Izquierdo, C. Gabaldón, J.M. Penya-roja
      The anaerobic degradation of 2-propanol, an important industrial solvent, was scaled-up from batch assays to a pilot expanded granular sludge bed (EGSB) reactor at 25°C. Batch studies indicated that 2-propanol followed Haldane kinetics, with a maximum rate at 10gCODL−1. Concentrations as high as 25gCODL−1 did not inhibit the degradation of ethanol, a common co-solvent. Similar specific methanogenic activities (SMA) were obtained for water-solvent and water-brewery sludges (88 and 77mlCH4 g-VS−1 d−1 at 5gCODL−1). Continuous degradation showed a lag-phase of three weeks with water-brewery sludge. Increases in 2-propanol load from 0.05 to 0.18kgCODkg-VS−1 d−1 caused a shift from the consumption of soluble matter to methane production, indicating polyhydroxybutyrates (PHB) accumulation. Conversely, smooth increases of up to 0.29kgCODkg-VS−1 d−1 allowed 2-propanol degradation without PHB accumulation. The slowdown rate of 2-propanol-oxidizer and acetate-utilizing methanogen bacteria below 20°C adversely impacted both removal and CH4 yield.

      PubDate: 2017-06-20T14:51:28Z
       
  • Adsorptive desulfurization of heavy naphthenic oil: Equilibrium and
           kinetic studies
    • Abstract: Publication date: 23 November 2017
      Source:Chemical Engineering Science, Volume 172
      Author(s): A.M. Moreira, H.L. Brandão, F.V. Hackbarth, D. Maass, A.A. Ulson de Souza, S.M.A. Guelli U. de Souza
      Models of adsorptive desulfurization to remove the major refractory sulfur compounds, such as thiophene (T), benzothiophene (BT) and dibenzothiophene (DBT) in decahydronaphthalene (DHN), were investigated. The experimental desulfurization of naphthenic oils using activated carbon was conducted in an adsorption system at different temperatures. The adsorptive capacity and selectivity of the adsorbent for sulfur compounds and the effects of coexisting inhibitors on the adsorption performance were examined. The activated carbon showed high capacity and selectivity in the adsorptive desulfurization of naphthenic oil. Water, carbazole, naphthalene and phenol in synthetic naphthenic oil have a strong inhibiting effect on the desulfurization performance of the adsorbent at 100°C. Increasing the temperature to 150°C can significantly improve the performance of the adsorbent in the desulfurization of real naphthenic oils. The results showed that the activated carbon exhibited a remarkable adsorption performance. The adsorption capacities reached 1.6×10−2, 2.0×10−2 and 1.9×10−2 kgkg−1 for T, BT and DBT in DHN, respectively. The Langmuir-Freundlich and Toth isotherm models provided good fits with the experimental equilibrium data for the real naphthenic oils. The kinetic results for the real naphthenic oils showed that the adsorption process can be described by a second-order mass transfer model. The results revealed that a temperature increase favors the sulfur adsorption kinetics and there was a greater diffusivity resistance for heavier oils. The data obtained showed effective diffusivity coefficients of between 7.5×10−15 and 2.6×10−13 m2 s−1 and mass transfer coefficients for the external fluid film ranging from 8.3×10−8 to 4.9×10−7 ms−1.
      Graphical abstract image

      PubDate: 2017-06-20T14:51:28Z
       
 
 
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